If you think that some of the descriptions of vampirism in Dracula seem creepily sexy, you're not alone. Most of the characters in Dracula are simultaneously attracted to and repulsed by the idea of having their blood sucked. Most of them are able to repress that desire most of the time, although they acknowledge the desire later in their journals. There aren't any actual sex scenes in the novel, but the blood-sucking scenes are close enough: they're described in terms of illicit desire and sexual repression.
The killing of Lucy by the Crew of Light, led by her fiancé, Arthur Holmwood, represents a male desire to repress female sexuality.
Mina is tainted by her contact with Dracula not so much because of his vampirism, but because her contact with him has made her sexually impure.